Recent years have witnessed a trend toward year-on-year increases in the amount of data handled by computer systems, and such increases in the amount of data have been handled by adding new storage apparatuses and migrating data between existing storage systems.
The units of the data migrated between storage systems are units of storage areas which are used by the host computer to store data in the storage apparatuses, namely, for example, logical volumes which are configured from a single hard disk drive (HDD), logical volumes in RAID (Redundant Arrays of Independent Disks) groups configured from a plurality of hard disk drives, or virtual logical volumes (hereinafter called ‘virtual volumes’) utilizing Thin Provisioning, and the like.
Here, Thin Provisioning is a function which provides virtual volumes to a host computer and which, when there is a request from the host computer to write data to a virtual volume, dynamically assigns a physical storage area for storing data to the virtual volume. With such Thin Provisioning, a virtual volume which has a greater capacity than the storage area which is actually available can be provided to the host apparatus. Furthermore, most recently, storage management has been efficiently performed by using hard disk drives of a plurality of types of varying performance. For example, according to a management technique known as hierarchical storage management (HSM), storage area is assigned from a high-speed, high-performance storage tier to an area where data of a high access frequency is stored and storage area is assigned from a low-speed, low-performance storage tier to an area where data of a low access frequency is stored.
Furthermore, PTL1 discloses a technology whereby information of a migration-source storage area in which migrated data is stored and information of a data migration-destination storage area are acquired and whereby the time required to migrate the data is calculated and an optimal data migration plan is created. For example, the migration of data of a high access frequency can be migrated by prioritizing the migration of data stored in a high-performance storage tier over the migration of data stored in a low-performance storage tier.